clone: support unusual remote ref configurations

When cloning a branchless and tagless but not refless remote using
protocol v0 or v1, Git calls transport_fetch_refs() with an empty ref
list. This makes the clone fail with the message "remote transport
reported error".

Git should have refrained from calling transport_fetch_refs(), just like
it does in the case that the remote is refless. Therefore, teach Git to
do this.

In protocol v2, this does not happen because the client passes
ref-prefix arguments that filter out non-branches and non-tags in the
ref advertisement, making the remote appear empty.

Note that this bug concerns logic in builtin/clone.c and only affects
cloning, not fetching.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/t/t5700-protocol-v1.sh b/t/t5700-protocol-v1.sh
index 468bd3e13e..6c8d4c6cf1 100755
--- a/t/t5700-protocol-v1.sh
+++ b/t/t5700-protocol-v1.sh
@@ -149,6 +149,21 @@ test_expect_success 'push with file:// using protocol v1' '
 	grep "push< version 1" log
 '
 
+test_expect_success 'cloning branchless tagless but not refless remote' '
+	rm -rf server client &&
+
+	git -c init.defaultbranch=main init server &&
+	echo foo >server/foo.txt &&
+	git -C server add foo.txt &&
+	git -C server commit -m "message" &&
+	git -C server update-ref refs/notbranch/alsonottag HEAD &&
+	git -C server checkout --detach &&
+	git -C server branch -D main &&
+	git -C server symbolic-ref HEAD refs/heads/nonexistentbranch &&
+
+	git -c protocol.version=1 clone "file://$(pwd)/server" client
+'
+
 # Test protocol v1 with 'ssh://' transport
 #
 test_expect_success 'setup ssh wrapper' '